A collision involving three vehicles occurred on Canal Road in Bradford on Saturday morning.
Emergency services were dispatched to the scene near the ACW Garden Centre at 9.42am.
The vehicles involved were identified as a grey Volkswagen Golf, a black Volvo, and a Lambretta motor scooter.
The scooter rider, a man aged 61, sustained serious injuries and was transported to hospital for medical treatment.
His condition has been described as critical but stable.
The driver of the Golf, a 24-year-old man, participated in a police interview under caution.
Investigations into the incident remain ongoing.
West Yorkshire Police are urging anyone who witnessed the collision or events preceding it, including dashcam footage, to come forward.
Those with relevant information can report it through the force website.
Investigators have requested that submissions include reference number 13260548392.